[This paper was actually written by Dumas alone, who was laboring under the mistaken impression that he and Liebig were finally in agreement. Soon Dumas was to part ways from Liebig for good by abandoning the radical theory (the panacea advocated in this paper) in favor of his compatriot Gerhard's unitary, or type, or substitution theory. I love Dumas's flowery language and his naïve assumptions that at long last all important theory is available so that we only need to get everyone else to agree and help in fleshing out our ideas with routine experimental results. This is a recurrent naïve theme in science generally (cf. the Human Genome Project). We always need more imagination.]
Meeting of Monday, 23 October, 1837
Note on the Present State of Organic Chemistry ;
by MM. Dumas and Liebig
Sixty years have hardly passed since the ever memorable time when this same assembly heard the first discussions of the fertile chemical doctrine which we owe to the genius of Lavoisier. This short span of time has sufficed to examine fully the most delicate questions of inorganic chemistry, and anyone can easily convince himself that this branch of our knowledge possesses almost everything that it can with the methods of observation available.
This is not only an incontestable fact, but one which is easily understood. Inorganic chemistry in fact concerns the story of elements and of their binary combinations and of their saline combinations. Now, elements divide into several very natural groups such that if one carefully studies the properties of one of the examples of a group, one can nearly always foresee and predict the properties of neighboring examples. The study of oxygen teaches us the story of sulfur; that of chlorine suffices to introduce us to the most minute details of the properties of iodine, etc.
Thus this task, which at first appeared beyond human ability, since it consisted of no less than studying and analyzing thousands of substances of quite diverse appearance and properties, this task was nevertheless completed in less than half a century, and there barely remain a few cracks here and there to fill in.
Chemists have realized that among inorganic substances there exist bodies which behave like elements; that these bodies combine with one another; that their combinations can themselves combine; and in these three orders of substances they have found a way of arranging natural groups which makes the study simple and easy and at the same time broad and philosophical.
Of course what they have called an element or an indecomposable body has only been considered as such with respect to the present state of experiment. They have not wished to prejudge the question at all; but have sought to construct the edifice of science in such a way that, if these elements are subsequently decomposed, nothing would be changed in the monument's architecture, although its foundations would be sunk deeper.
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It is easy to understand that with the fifty-four elements recognized today one can, with the help of a very small number of combining laws and by forming all the binary combinations or all the possible salts, create not only all the known compounds of inorganic chemistry but create besides a very large number of analogous compounds.
But how can one apply such notions successfully to organic chemistry? Here one encounters no fewer substances than in inorganic chemistry, and they are no less diverse. Here, however, instead of fifty-four elements one encounters hardly more than three or four in most known compounds. In a word, how with the help of the laws of inorganic chemistry can one explain and classify such varied substances as one obtains from organic bodies, and which nearly always are formed only of carbon, hydrogen, and oxygen, to which elements nitrogen is sometimes joined?
This was the great and beautiful question of natural philosophy, a question well designed to excite the highest degree of competition among chemists; for once resolved the most beautiful triumphs were promised to science. The mysteries of plants, the mysteries of animal life would be unveiled before our eyes; we would seize the key to all the changes of matter, so sudden, so swift, so singular, that occur in animals and plants; more importantly we would find the means of duplicating them in our laboratories.
Well, we are not afraid to say it, and it is not an assertion which we make lightly: this great and beautiful question is today answered; it only remains to follow through on all the consequences which its solution entails. Certainly if before experiment had opened this new route one had asked a chemist for his opinion on the nature of organic substances, however great his genius he could have imagined nothing, one can be sure, which would be worthy of being compared with these simple, regular, beautiful laws which experiment has unveiled over several years.
In fact to produce with three or four elements such varied combinations, more varied perhaps than those which make up the whole inorganic kingdom, nature has chosen a path as simple as it was unexpected; for with elements she has made compounds which behave in all their properties like elements themselves.
And this, we are convinced, is the entire secret of organic chemistry.
Thus organic chemistry possesses its own elements, which sometimes play the role of chlorine or oxygen in inorganic chemistry and sometimes, on the contrary, play the role of metals. Cyanogen, amide, benzoyl, the radicals of ammonia, of aliphatics, of alcohol, and analogous substances, these are the true elements with which organic chemistry operates and not the ulterior elements, carbon, hydrogen, oxygen, nitrogen, elements which only appear after all trace of the organic origin has disappeared.
For us inorganic chemistry embraces all substances which result from direct combination of true elements.
Organic chemistry, by contrast, must include all substances formed from compound bodies functioning as elements would.
In inorganic chemistry the radicals are simple; in organic chemistry they are compound, that is the whole difference. The combining laws, the laws of reaction are otherwise identical in the two branches of chemistry.
Perhaps we could add, as a view of the future which is permitted from a philosophical point of view, that the less advanced of the two chemistries which we have just defined is not the one we might imagine.
In fact if the radicals of inorganic chemistry, if oxygen, if sulfur, if the metals are compound bodies, no one could predict when and how their decomposition could be realized. If it be possible, this decomposition requires powers which are unknown to us.
In organic chemistry the difficulty is much less, and it is precisely the opposite. Here the radicals are in fact compound; as we know. All art in organic chemistry consists of handling them while avoiding the destruction which would take them back to the inorganic state, that is to the state of truly indecomposable elements. This passage of compound organic elements to their simple inorganic elements can be foreseen and prevented; since it takes place according to easily grasped laws. Also it is almost always possible to recognize an organic radical and to make it pass from one compound to another without its resolution into inorganic elements.
In our view, organic chemistry thus presents us radicals which play the same role as metals, others which play a role analogous to oxygen, chlorine, or sulfur, etc. These radicals combine with one another or with true elements, thus giving rise, by means of the simplest laws of inorganic chemistry, to all organic compounds.
To discover these radicals, to study them, to characterize them, this has been our daily study for ten years. Inspired by the same hope, running along the same path, using the same techniques, it has been rare that we have not simultaneously studied the same or very similar substances, and that we have not seen the facts which presented themselves to us from the same point of view. Sometimes, none the less, our opinions have appeared to differ, and then, with each of us drawn on by the heat of our battle with nature, there arose between us discussions whose liveliness we both regret. Who could deny, however, the utility of these discussions, their necessity? Who could say how many beautiful investigations they caused, and how many they still cause? In each young science such debates always arise; but what is perhaps novel in the history of science is the manner in which we have judged it convenient to conclude them.
Actually when we were able to discuss questions which separated us in several friendly meetings, we soon realized that we were in agreement on the principles, and on the application we differed so little that it would be easy to reach agreement.
We then understood that united we could undertake a task before which either of us in isolation would have recoiled; this is the natural classification of organic substances; this is a deeper discussion of which radicals it is necessary to recognize and a laying out of their direct and secondary characteristics; this is, in a word, the chemical philosophy of organic substances.
Here is the plan we propose to follow:
We will analyze every organic substance, if it has not already been analyzed. We will carefully verify all analyses published by chemists interested in this sort of question, and we ask them to submit ours to the same tests. Nothing is more important for everyone than reliable analyses, which may be used with perfect confidence in systematic schemes, which subsequent experiments can confirm, and which may serve as a point of departure for the happiest investigations.
But these numerous analyses, these patient checks are only the least of the task we impose on ourselves. Our principal goal being to characterize each body, to establish reliably what sort of radical it refers to, we will devote all our care to elucidating the reactions themselves of each substance which we study.
Thus the elemental analysis of each substance, the determination of its atomic weight, the study of its principal reactions, these are the subjects of our work. The discussion of the characteristics observed in this way and the establishment of compound radicals by which these characteristics may be explained, these are the end toward which this work is directed.
But those who know how many substances are already included in organic chemistry, and how many more are being discovered daily, these individuals will regard our project as a foolish fancy, if they are familiar with the difficulties which the smallest research in organic chemistry so often raises for those who undertake it.
Thus, despite all our ardor for the work! despite all the effort which we are certain to devote to it, we would have judged it absolutely necessary greatly to restrict the general plan we have just outlined, if we had not long ago taken care to prepare collaborators whose zeal will not fail our attempt.
Each of us has, in fact, opened his laboratory to all young men who were motivated by true love of science; they have seen all, understood all. We have worked under their eyes, and have had them work under ours, in such a way that we are surrounded by young rivals, who are the hope of science, and whose work will be added to ours and mingle with ours, for it will have been conceived in the same spirit and carried out by the same methods.
By this happy cooperation, among a circle which we try daily to expand, we hope for a propitious ending to the work which we will undertake.
Let us add that in a study as delicate as that to which we are devoting ourselves we have great need to be helped by anyone who can provide us with organic products which are remarkable for their purity, their crystallinity, and the authenticity of their origin. We are confident in addressing this request to all friends of science, and we dare hope that this desire will not have been expressed in vain.
Besides, this is not an effort conceived for personal gain or in the interest of narrow vanity. No, and in a collaboration which is perhaps unheard of in the history of science, this is an undertaking in which we hope to interest every chemist in Europe.
Actually the British Association for the Advancement of Science, at its last meeting in Liverpool, expressed the wish that an overview of the present state of organic chemistry be presented to it by M. Liebig and myself at its next meeting. Thus the cooperation and good will of the English scientists are obtained for our work.
The position of M. Liebig assures us of the goodwill of the northern European chemists. As for myself, I have not thought that I went too far in promising the cooperation of the French chemists and in giving assurances that the Academy would lend all its influence to our research and that it would receive this communication with the goodwill of which it has already shown us so many signs.